1. Field of the Invention
The present invention relates to a display apparatus for automobiles which is installed at an instrument panel for indicating information on driving conditions for a driver.
2. Description of the Prior Art
Conventionally, a display apparatus for automobiles is proposed, which utilizes reflection surfaces for displaying an image at a long distance to increase the speed for recognizing the displayed image.
In this display apparatus for automobiles, since a longer optical path after reflection shows a better far-point-display function, as described in FIG. 5, a display apparatus for automobiles has been proposed in which light is reflected by two surfaces so that the optical path of the reflected light is lengthened while reducing the space occupied by the reflected light.
In FIG. 5, denoted 21 is a self-emission-type indicator such as a liquid crystal display and a vacuum fluorescent tube, 22 a semi-transparent plate as a reflection plate with a reflection surface 22A formed of dark transparent acrylic smoked plate, 23 a total reflection mirror with a total reflection surface 23A opposing the semi-transparent reflection plate 22, and 24 a meter hood integrally formed with an instrument panel. The indicator 21, the semi-transparent reflection plate 22, and the total reflection mirror 23 are installed in the instrument panel. The semi-transparent reflection plate 22 is diagonally arranged in such a manner as to have an angle between the plate and the total reflection mirror 23 smaller than 45.degree..
A dashed line in the figure represents a ray which is emitted from the indicator 21 and finally reaches the viewfield 25. A display light projected by the indicator 21 transmits through semi-transparent reflection plate 22 and falls on the total reflection mirror 23 to be reflected by the total reflection mirror 23. Then, the light is further reflected by the reflection surface 22A of the semi-transparent reflection plate 22 to be directed to the viewfield 25. Therefore, when seen from the viewfield 25, behind the reflection surface 22A of the semi-transparent reflection plate 22 is recognized a virtual image of the display.
In this case, the recognized virtual image is positioned in the range that the display light is reflected by the reflection surface 23A of the total reflection mirror 23 via the reflection surface 22A to reach the viewfield and the virtual image is displayed at a long distance by repeated reflection so that a clear displayed image is obtained. Further, the semi-transparent reflection plate is darkish and the reflection surface 22A thereof is not a total reflection surface, allowing a displayed image to be recognized on the dark background.
The meter hood 24 interrupts external light S from an upside like an ordinary meter hood and prevents the display by the reflected light within the range B from washout. The range B (hereinafter called as "display range") is defined as the range that the reflection surface 23A is seen from the viewpoint 25 via the reflection surface 22A.
However, in the display apparatus described above having two reflection surfaces 22A and 23A, as exemplified in FIG. 5a line of sight passing through the upper optical path in the range that the display range B is seen from the viewfield 25 is directed to an optical path Q on the driver's side since the line of sight is repeatedly reflected by the reflection surfaces 22A and 23A. Accordingly, external light may be seen on the background because a view on the driver's side is recognized, causing a problem that the quality of the displayed image is deteriorated.